I've been out-of-the-loop for a while, what's the state of the art in re: OpenAPI/Swagger? What I mean is, are people using it in the wild? Are there mature (

I've been out-of-the-loop for a while, what's the state of the art in re: OpenAPI/Swagger? What I mean is, are people using it in the wild? Are there mature (or at least pretty stable) code generators? Test generators? What's inter-operability like? (Is it easy/possible to generate clients and server stubs in different languages that will work together? Can I write a service, publish my API spec, and expect people to be able to use it to write clients?)